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Lanthanum Chloride
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Beuchat
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INTRODUCTION
All reef aquarium enthusiasts are aware of the importance of maintaining nitrate and phosphate concentrations within recommended ranges. Excess or deficiency of phosphate in aquarium water has undesirable consequences for the growth and health of corals and other invertebrates. Elevated phosphate levels inhibit coral calcification and increase the persistence of algae pests, while undetectable concentrations promote the emergence of dinoflagellates and cyanobacteria. Numerous techniques exist to keep phosphate concentration within reasonable limits, such as using GFO or organic carbon dosing, which greatly helps with dinoflagellates. Lanthanum chloride is one of these techniques and stands out for its extraordinary potency and speed, which can be a drawback depending on the type of aquarium and the situation.
LANTHANUM TOXICITY
Lanthanum has a certain level of toxicity for the organisms in our aquariums. For instance, a study investigated the toxicity of lanthanum for the embryos of the sea urchin Paracentrotus lividus (Oral et al., 2012). A concentration of 1.38 mg/L did not cause embryo mortality but resulted in developmental defects in all cases. When the concentration of lanthanum was reduced to 0.138 mg/L, only 10% of the examined embryos presented defects.
In other laboratory experiments, it has been verified that zooplankton organisms like Daphnia carinata suffer adverse effects at lanthanum doses above 0.043 mg/L and die at concentrations exceeding 0.08 mg/L. This toxicity has been used as a tool to eradicate parasitic flatworm pests in acroporas (AEFW). When lanthanum became popular as a phosphate control tool in aquariums, some hobbyists using the lanthanum observed that it caused the death of flatworms of the genera Waminoa and Convolutriloba as a side effect. Dr. Samuel Nietzer, a coral biology researcher at the University of Oldenburg, indicated that the toxic effect of lanthanum on flatworms has been known and used for a long time. Daniel Knop indicated a toxic concentration threshold in aquariums of 138 μg/L, which can be verified using an ICP test. In a study he conducted some time ago, he showed that a small amount of unreacted lanthanum always remained in the water (verified by ICP).
MECHANISM
Lanthanum ions combine with dissolved phosphate ions in the water, forming lanthanum phosphate, which precipitates as solid flocs. This removes phosphate from the aquarium water. It is important to note that if no method is implemented to export the flocs, they deposit in the substrate, rocks, or mechanical filters. This is not a major problem, as the flocs cannot dissolve at the typical pH of a reef tank unless they pass through a calcium reactor, for example, where the pH is around 6.3.
One way to avoid this effect is by using a lanthanum reactor. This is a very simple device, essentially a fluidized bed reactor filled with mechanical filtration media such as polyester wool. A medium-flow pump draws water from the sump and passes it through the device. At some point, there is a T-connection where lanthanum chloride solution is injected using a dosing pump. The flocs form inside the reactor and are trapped by the polyester wool. When the hobbyist detects the saturation of the media, it is replaced.
Due to the extraordinary potency and speed of this method, as phosphate removal is instantaneous, it must be used with great caution. A very small amount of lanthanum chloride is enough to quickly reduce the phosphate concentration in the tank. Commercial products can achieve a phosphate reduction of 0.1 mg/L in water with an application of 1 mL per 100 liters of aquarium water, which is truly impressive. There is some risk of causing too rapid and excessive a drop, which can stress corals and encourage an outbreak of dinoflagellates and cyanobacteria.
HOMEMADE SOLUTION
It is easy to prepare a homemade lanthanum chloride solution. To do this, dissolve 9 grams (~2 level teaspoons) of lanthanum chloride heptahydrate in water to make 500 mL in total. 1 mL of this solution removes 4.6 mg of phosphate in the aquarium.
RECOMMENDATIONS
Lanthanum chloride works very well in aquariums with a high external food input, such as those maintaining non-photosynthetic corals. However, it is not suitable for tanks with very low phosphate concentrations, such as ULNS (ultra-low nutrient systems). The reason is that when phosphate ions are insufficiently available, lanthanum combines with carbonate ions, producing lanthanum carbonate flocs, which can result in a drop in alkalinity depending on the dosage and aquarium size. Alkalinity also decreases after dosing because corals calcify more rapidly when less phosphate is available in the water. Therefore, it makes sense to use lanthanum to reduce the concentration to "manageable" levels and subsequently maintain it using organic carbon or resins. Always ensure not to drop below 0.03 mg/L. The risk of lanthanum is twofold: it can cause excessive reduction and, on the other hand, the speed of that reduction.
Currently, the addition of lanthanum chloride without using an external reactor is commonly practiced by many hobbyists without apparent negative effects. The risks of toxicity seem to be lower than initially thought. In any case, the debate is active within the hobbyist community. If not using a reactor, the recommendation would be to dose lanthanum just before mechanical filters such as socks, rollermats, or skimmers. In this sense, the overflow is a good location. It is advisable to use low and regular doses of the solution while monitoring phosphate concentrations. Monitoring is essential to ensure that water conditions do not change too quickly, as this always has an adverse effect on corals. Phosphate concentration reduction must be measurable and traceable, and the concentration of free lanthanum in the aquarium water should not increase too much, as its possible harmful effects, particularly on corals, anemones, and other invertebrates, are not well understood. A good routine could be to use lanthanum when phosphate concentrations rise above 0.2 mg/L.
We emphasize the need to dose in very small amounts throughout the day, the smaller, the better. If the solution is added directly to the aquarium, the flocs can cause turbidity in the water, and fish, during respiration, can absorb them through their gills, where there is a very low pH due to CO2 excretion. This can cause the flocs to dissolve, leading to lanthanum intoxication. In fact, some cases of fish fatalities have been reported following the addition of lanthanum chloride.
All reef aquarium enthusiasts are aware of the importance of maintaining nitrate and phosphate concentrations within recommended ranges. Excess or deficiency of phosphate in aquarium water has undesirable consequences for the growth and health of corals and other invertebrates. Elevated phosphate levels inhibit coral calcification and increase the persistence of algae pests, while undetectable concentrations promote the emergence of dinoflagellates and cyanobacteria. Numerous techniques exist to keep phosphate concentration within reasonable limits, such as using GFO or organic carbon dosing, which greatly helps with dinoflagellates. Lanthanum chloride is one of these techniques and stands out for its extraordinary potency and speed, which can be a drawback depending on the type of aquarium and the situation.
LANTHANUM TOXICITY
Lanthanum has a certain level of toxicity for the organisms in our aquariums. For instance, a study investigated the toxicity of lanthanum for the embryos of the sea urchin Paracentrotus lividus (Oral et al., 2012). A concentration of 1.38 mg/L did not cause embryo mortality but resulted in developmental defects in all cases. When the concentration of lanthanum was reduced to 0.138 mg/L, only 10% of the examined embryos presented defects.
In other laboratory experiments, it has been verified that zooplankton organisms like Daphnia carinata suffer adverse effects at lanthanum doses above 0.043 mg/L and die at concentrations exceeding 0.08 mg/L. This toxicity has been used as a tool to eradicate parasitic flatworm pests in acroporas (AEFW). When lanthanum became popular as a phosphate control tool in aquariums, some hobbyists using the lanthanum observed that it caused the death of flatworms of the genera Waminoa and Convolutriloba as a side effect. Dr. Samuel Nietzer, a coral biology researcher at the University of Oldenburg, indicated that the toxic effect of lanthanum on flatworms has been known and used for a long time. Daniel Knop indicated a toxic concentration threshold in aquariums of 138 μg/L, which can be verified using an ICP test. In a study he conducted some time ago, he showed that a small amount of unreacted lanthanum always remained in the water (verified by ICP).
MECHANISM
Lanthanum ions combine with dissolved phosphate ions in the water, forming lanthanum phosphate, which precipitates as solid flocs. This removes phosphate from the aquarium water. It is important to note that if no method is implemented to export the flocs, they deposit in the substrate, rocks, or mechanical filters. This is not a major problem, as the flocs cannot dissolve at the typical pH of a reef tank unless they pass through a calcium reactor, for example, where the pH is around 6.3.
One way to avoid this effect is by using a lanthanum reactor. This is a very simple device, essentially a fluidized bed reactor filled with mechanical filtration media such as polyester wool. A medium-flow pump draws water from the sump and passes it through the device. At some point, there is a T-connection where lanthanum chloride solution is injected using a dosing pump. The flocs form inside the reactor and are trapped by the polyester wool. When the hobbyist detects the saturation of the media, it is replaced.
Due to the extraordinary potency and speed of this method, as phosphate removal is instantaneous, it must be used with great caution. A very small amount of lanthanum chloride is enough to quickly reduce the phosphate concentration in the tank. Commercial products can achieve a phosphate reduction of 0.1 mg/L in water with an application of 1 mL per 100 liters of aquarium water, which is truly impressive. There is some risk of causing too rapid and excessive a drop, which can stress corals and encourage an outbreak of dinoflagellates and cyanobacteria.
HOMEMADE SOLUTION
It is easy to prepare a homemade lanthanum chloride solution. To do this, dissolve 9 grams (~2 level teaspoons) of lanthanum chloride heptahydrate in water to make 500 mL in total. 1 mL of this solution removes 4.6 mg of phosphate in the aquarium.
RECOMMENDATIONS
Lanthanum chloride works very well in aquariums with a high external food input, such as those maintaining non-photosynthetic corals. However, it is not suitable for tanks with very low phosphate concentrations, such as ULNS (ultra-low nutrient systems). The reason is that when phosphate ions are insufficiently available, lanthanum combines with carbonate ions, producing lanthanum carbonate flocs, which can result in a drop in alkalinity depending on the dosage and aquarium size. Alkalinity also decreases after dosing because corals calcify more rapidly when less phosphate is available in the water. Therefore, it makes sense to use lanthanum to reduce the concentration to "manageable" levels and subsequently maintain it using organic carbon or resins. Always ensure not to drop below 0.03 mg/L. The risk of lanthanum is twofold: it can cause excessive reduction and, on the other hand, the speed of that reduction.
Currently, the addition of lanthanum chloride without using an external reactor is commonly practiced by many hobbyists without apparent negative effects. The risks of toxicity seem to be lower than initially thought. In any case, the debate is active within the hobbyist community. If not using a reactor, the recommendation would be to dose lanthanum just before mechanical filters such as socks, rollermats, or skimmers. In this sense, the overflow is a good location. It is advisable to use low and regular doses of the solution while monitoring phosphate concentrations. Monitoring is essential to ensure that water conditions do not change too quickly, as this always has an adverse effect on corals. Phosphate concentration reduction must be measurable and traceable, and the concentration of free lanthanum in the aquarium water should not increase too much, as its possible harmful effects, particularly on corals, anemones, and other invertebrates, are not well understood. A good routine could be to use lanthanum when phosphate concentrations rise above 0.2 mg/L.
We emphasize the need to dose in very small amounts throughout the day, the smaller, the better. If the solution is added directly to the aquarium, the flocs can cause turbidity in the water, and fish, during respiration, can absorb them through their gills, where there is a very low pH due to CO2 excretion. This can cause the flocs to dissolve, leading to lanthanum intoxication. In fact, some cases of fish fatalities have been reported following the addition of lanthanum chloride.
Great review thanks! I use LC every week in a very large high PO4 tank, I am happy to knock the phosphates down to 0.1.
The bit about the calcium reactor was something I never considered. My feed pump lives in a filter sock... which hopefully prevents it from sucking any floc.
The bit about the calcium reactor was something I never considered. My feed pump lives in a filter sock... which hopefully prevents it from sucking any floc.
Miami Reef
10K Club Member
I just use GFO. The work and risk with lanthanum isn’t worth it for me.
I'm dosing lanthanum now for 2 years 0.6 mll per day ( 6 times 0.1 mll 24/7 ) at a 185 gallon tank.
Phosphate is always stabil at 0.08
I dose it 2" in front of the inlet of the skimmerpump.
Phosphate is always stabil at 0.08
I dose it 2" in front of the inlet of the skimmerpump.
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Miami Reef
10K Club Member
I put 2-3 tablespoons in my BRS reactor (260 gallon tank), flush a few seconds in a bucket, then put the output tube back in the water. There is an adjustment that helps you tune so the GFO can have a slight tumble.
Lanthanum can risk killing certain fish and potentially clog clam gills. It’s hard to remove the particles, and it isn’t known if free lanthanum is the issue (which there always will be) or if the precipitate is the issue.
I personally believe (although not sure if true) that lanthanum can precipitate onto coral skeletons which could possibly (unproven) reduce calcification.
All in all, it’s a lot of potential and theoretical risks. GFO is less risky and gives me the peace of mind. I don’t find it hard to work with at all.
@Randy Holmes-Farley Im not sure if I asked, but could you try to see if my concern with coral calcification concerns are valid? I don’t know if that’s true. It’s just a fear of mine since coral growth is a huge priority since I compete.
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I want to go this route. I’ve used GFO but it’s too erratic for me.
When it’s exhausted after about 6 weeks and I replace it, I can’t run it 24/7. It depletes the PO4 too fast and too much.
So I start with running it for about 8 hours a few days and then increase to 12 for a few days and then eventually 24. I have to test PO4 pretty regularly to make sure it doesn’t creep up again. Then when it does, rinse and repeat.
I want to be able to dose LC to keep a more consistent PO4 level. I’ve been using the diluted Phosban and it works well. No negative effects to any fish.
To get to your dosing amount, did you just do trial and error to get to the amount that’s needed for your desired PO4 reduction?
Miami Reef
10K Club Member
That doesn’t really make sense to me. GFO would deplete and bind much sooner than 6 weeks.
I would use significantly less and change it every 2-3 weeks as needed. I can keep my phosphate very stable with GFO.
How do you know when the GFO is exhausted? What level do you change it out? What’s your ideal phosphate level? Just curious.
It does but then as a result of feeding it rises each day. So the GFO brings it down and keeps it in check until it’s exhausted when I then need to change it out.
I test weekly so when PO4 starts to rise, it’s time to swap it out.
I like my PO4 to be in the .07-.10 range. Once it starts moving towards 1.5 I swap it out.
I test weekly so when PO4 starts to rise, it’s time to swap it out.
I like my PO4 to be in the .07-.10 range. Once it starts moving towards 1.5 I swap it out.
Miami Reef
10K Club Member
I’m going to assume you mean 0.15ppm.
I think the issue is that you use enough GFO to last you 6 weeks. GFO works really well at first, but then its effectiveness is greatly reduced once phosphate, organics, and bacteria clog the pores.
Have you ever considered using less GFO and changing it out every 2-4 weeks?
I think that will stop the extreme dip, and it will save you a lot of time since you are basically tuning it by the hours it runs.
Just a thought. You can use lanthanum if you’d like. Many people do, and many find it easier than GFO.
Oops, yes, 0.15.
I’ve thought about it and while it will reduce the initial dip, it will require switching out much more often. I doubt it would last me 4 weeks so 2 is more likely.
Given my desire to keep maintenance at a minimum and the fact that GFO aint cheap, I’m considering the LC option.
What are the numbers for your tank? PO4 levels, amount of GFO used, frequency of replacement, how do you know it’s time for replacement?
BTW, I currently use about 3 cups of high cap GFO.
Miami Reef
10K Club Member
Oh wow. I use 2 tablespoons of high capacity in my 260 gallon and it knocks my levels right down. We must have very different feeding inputs.
Lots of people use lanthanum. I’ll send you the lanthanum link (made by Randy) in case you ever wanted to give it a shot:
DIY Lanthanum Dosing
Someone asked for a DIY lanthanum dosing recipe. Be sure you understand that some folks have issues with fish (especially tangs) before embarking on lanthanum dosing. it is also preferable to catch as many of the solids that precipitate out as you can, so dosing before some sort of...
www.reef2reef.com
Lots of people share what method they use with lanthanum. It’s a very interesting thread with all the info you’ll need. You can post in that thread and Randy will likely answer your questions, too.
Thanks.Oh wow. I use 2 tablespoons of high capacity in my 260 gallon and it knocks my levels right down. We must have very different feeding inputs.
Lots of people use lanthanum. I’ll send you the lanthanum link (made by Randy) in case you ever wanted to give it a shot:
DIY Lanthanum Dosing
Someone asked for a DIY lanthanum dosing recipe. Be sure you understand that some folks have issues with fish (especially tangs) before embarking on lanthanum dosing. it is also preferable to catch as many of the solids that precipitate out as you can, so dosing before some sort of...
Lots of people share what method they use with lanthanum. It’s a very interesting thread with all the info you’ll need. You can post in that thread and Randy will likely answer your questions, too.
Hoping Jack will weigh in as it seems his method is what I’m after.
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